A set of files that record all changes made to an Oracle database. A database MUST have at least two redo log files. Log files can be multiplexed on multiple disks to ensure that they will not get lost.

Query redo log details:

SELECT * FROM v$log;

To see the logfile members:

SELECT * FROM v$logfile;

Note that a redo log can have different states:

CURRENT: redo records are currently being written to the group. Only one group is current at a time.